As per Dan69's comment - how are you setting both your RAM timings and voltage? D.O.C.P (AMD's version of XMP) is not the way to do it. You need to set the following primary timings manually in BIOS to whatever G.Skill has noted for your model of RAM:
TCL, TRCD, TRP, TRAS, TRC.
Also you should manually set your RAM to its rated speed in the appropriate menu within BIOS (AI tweaker menu, memory frequency option)
In addition you need to go into the relevant menu and manually increase your DRAM voltage by hitting the '+' key and upping it to say 1.355v or whatever your're comfortable with.
Apologies if you have done all this, but you do not say so I have to assume you have just tried to set the DOCP speed, which is not going to provide the stability your looking for.